Sodium iridate
Chemical compound
From Wikipedia, the free encyclopedia
Sodium iridate (chemical formula Na3Ir3O8) is a sodium–iridium oxide that is geometrically frustrated, making it a strongly spin–orbit-coupled transition-metal oxide.[3] It is described as a hyperkagome iridate related to Na4Ir3O8, whose hyperkagome lattice is a three-dimensional network of corner-sharing triangular units.[4] Na3Ir3O8 is described as a 1/3-doped analogue of Na4Ir3O8 (average Ir valence ≈ +4.33) and as semimetallic compared with the more insulating hyperkagome parent compound.[3][5]
Crystal structure of sodium iridium oxide Na 3Ir 3O 8. Cyan spheres show the Ir hyperkagome network; red spheres are oxygen atoms; polyhedra indicate two Na coordination environments. | |
| Properties | |
|---|---|
| Na 3Ir 3O 8 | |
| Molar mass | 773.61 g/mol |
| Density | 7.50 g/cm3[1] |
| Structure | |
| cubic[2] | |
| P4132 (No. 213)[2] | |
Formula units (Z) |
4[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Structure
Hyperkagome iridates are discussed as spinel-related (ordered-spinel) materials in which the Ir sublattice forms a three-dimensional network of corner-sharing triangles (the hyperkagome lattice).[5][4] The hyperkagome can be viewed as a "deleted" pyrochlore-type network obtained by removing one-quarter of sites from a pyrochlore lattice.[4][5] In iridates with Ir4+ (5d5), strong spin–orbit coupling entangles spin and t2g orbital character into effective Jeff = 1/2 moments, which is often used to motivate spin-liquid proposals for the hyperkagome lattice.[5][3] Na3Ir3O8 is described as a chiral, frustrated hyperkagome system and is commonly discussed as a doped member within the Na4−xIr3O8 family. Partial Na deintercalation from Na4Ir3O8 can lead to a doped hyperkagome with Na3Ir3O8 as an end member.[3][5]
Physical properties
Na3Ir3O8 demonstrates strong spin–orbit coupling combined with lattice-driven electronic-structure effects (including distortion-induced molecular orbitals in the hyperkagome setting).[3][5] Because it combines a frustrated lattice with strong spin–orbit coupling and chiral structure, it has been suggested as a platform to explore unconventional electronic transport, including possible topological contributions.[3]